- progress towards client agent forwarding

(incomplete and does not compile)

1 files changed, 245 insertions, 0 deletions

diff --git a/cli-agentfwd.c b/cli-agentfwd.c
new file mode 100644
index 0000000..f0fe385
--- /dev/null
+++ b/cli-agentfwd.c
@@ -0,0 +1,245 @@
+/*
+ * Dropbear - a SSH2 server
+ * 
+ * Copyright (c) 2005 Matt Johnston
+ * All rights reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE. */
+
+/* The basic protocol use to communicate with the agent is defined in
+ * draft-ylonen-ssh-protocol-00.txt, with the ssh2 extensions defined through
+ * openssh's implementation. */
+
+#include "includes.h"
+
+#ifdef ENABLE_CLI_AGENTFWD
+
+#include "agentfwd.h"
+#include "session.h"
+#include "ssh.h"
+#include "dbutil.h"
+#include "chansession.h"
+#include "channel.h"
+#include "packet.h"
+#include "buffer.h"
+#include "random.h"
+#include "listener.h"
+#include "runopts.h"
+#include "atomicio.h"
+#include "signkey.h"
+#include "auth.h"
+
+static int new_agent_chan(struct Channel * channel);
+
+const struct ChanType chan_cli_agent = {
+	0, /* sepfds */
+	"auth-agent@openssh.com",
+	new_agent_chan,
+	NULL,
+	NULL,
+	NULL
+};
+
+static int connect_agent() {
+
+	int fd = -1;
+	char* agent_sock = NULL;
+
+	agent_sock = getenv("SSH_AUTH_SOCK");
+	if (agent_sock == NULL)
+		return -1;
+
+	fd = connect_unix(agent_sock);
+
+	return fd;
+}
+
+// handle a request for a connection to the locally running ssh-agent
+// or forward.
+static int new_agent_chan(struct Channel * channel) {
+
+	int fd = -1;
+
+	if (!cli_opts.agent_fwd)
+		return SSH_OPEN_ADMINISTRATIVELY_PROHIBITED;
+
+	fd = connect_agent();
+
+	setnonblocking(fd);
+
+	ses.maxfd = MAX(ses.maxfd, fd);
+
+	channel->infd = fd;
+	channel->outfd = fd;
+
+	// success
+	return 0;
+}
+
+/* Sends a request to the agent, returning a newly allocated buffer
+ * with the response */
+/* Packet format (from draft-ylonen)
+   4 bytes     Length, msb first.  Does not include length itself.
+   1 byte      Packet type.  The value 255 is reserved for future extensions.
+   data        Any data, depending on packet type.  Encoding as in the ssh packet
+   protocol.
+
+ In this case, data is always empty
+*/
+static buffer * agent_request(int fd, unsigned char type) {
+
+	buffer * payload = NULL;
+	buffer * inbuf = NULL;
+	size_t readlen = 0;
+	ssize_t ret;
+
+	payload = buf_new(4 + 1);
+
+	buf_putint(payload, 1);
+	buf_putbyte(payload, type);
+
+	ret = atomicio(write, fd, buf_getptr(payload, payload->len), payload->len);
+	if ((size_t)ret != payload->len) {
+		TRACE(("write failed for agent_request"))
+		goto out;
+	}
+
+	buf_free(payload);
+	payload = NULL;
+
+	/* Now we read the response */
+	inbuf = buf_new(4);
+	ret = atomicio(read, fd, buf_getwriteptr(inbuf, 4), 4);
+	if (ret != 4) {
+		TRACE(("read of length failed for agent_request"))
+		goto out;
+	}
+
+	readlen = buf_getint(inbuf);
+	if (readlen > MAX_AGENT_REPLY) {
+		TRACE(("agent reply is too big"));
+		goto out;
+	}
+
+	buf_resize(inbuf, readlen);
+	ret = atomicio(read, fd, buf_getwriteptr(inbuf, readlen), readlen);
+	if ((size_t)ret != readlen) {
+		TRACE(("read of data failed for agent_request"))
+		goto out;
+	}
+
+out:
+	if (payload)
+		buf_free(payload);
+
+	return inbuf;
+}
+
+static SignKeyList * agent_get_key_list(int fd)
+{
+	buffer * inbuf = NULL;
+	unsigned int num = 0;
+	unsigned char packet_type;
+	unsigned int i;
+	struct SignKeyList *retkey = NULL, *key = NULL;
+	int ret;
+
+	inbuf = agent_request(fd, SSH2_AGENTC_REQUEST_IDENTITIES);
+	if (!inbuf) {
+		goto out;
+	}
+
+	/* The reply has a format of:
+	 * byte     packet_type
+	 * int      num_keys
+	 *
+	 * string    keyblob1
+	 * string    comment1
+	 * ...
+	 * string    keyblob(n)
+	 * string    comment(n)
+	 */
+	packet_type = buf_getbyte(inbuf);
+	if (packet_type != SSH2_AGENT_IDENTITIES_ANSWER) {
+		goto out;
+	}
+
+	num = buf_getint(inbuf);
+	for (i = 0; i < num; i++) {
+		sign_key * pubkey = NULL;
+		char key_type = DROPBEAR_SIGNKEY_ANY;
+		struct SignKeyList *nextkey = NULL;
+
+		nextkey = (struct SignKeyList*)m_malloc(sizeof(struct SignKeyList));
+		if (key)
+			key->next = nextkey;
+		else
+			retkey = nextkey;
+		key = nextkey;
+
+		pubkey = new_sign_key();
+		ret = buf_get_pub_key(inbuf, pubkey, &key_type);
+		if (ret != DROPBEAR_SUCCESS) {
+			/* This is slack, properly would cleanup vars etc */
+			dropbear_exit("Bad pubkey received from agent");
+		}
+
+		key->key = pubkey;
+		key->next = NULL;
+		key->type = key_type;
+		key->source = SIGNKEY_SOURCE_AGENT;
+
+		/* We'll ignore the comment */
+		buf_eatstring(inbuf);
+	}
+
+out:
+	if (inbuf) {
+		buf_free(inbuf);
+		inbuf = NULL;
+	}
+
+	return retkey;
+}
+
+/* return DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
+SignKeyList * load_agent_keys()
+{
+
+	SignKeyList * ret_list;
+	int fd;
+	fd = connect_agent();
+	if (fd < 0) {
+		dropbear_log(LOG_INFO, "Failed to connect to agent");
+		return NULL;
+	}
+
+	ret_list =  agent_get_key_list(fd);
+	close(fd);
+}
+	
+// general procedure:
+// - get the list of keys from the agent
+// - foreach, send a dummy userauth_pubkey message to the server and see
+// if it lets us in
+// - if it does, sign and auth
+// - if not, repeat.
+//
+
+#endif